Controls for refrigeration systems



y 1967 J. R. HARNISH 3,320,763

CONTROLS FOR REFRIGERATION SYSTEMS Filed Nov. 19, 1965 FIG'L IOEVAPORATOR COR ACCUMULATOR JCONDENSE con.

c --HERMET|C l5 COMPRESSOR 5| 2 24 m 55 l A 59 BALL |NVENTOR= JAMESRHARNISH, BYW 17. 9%

ATTORNEY United States Patent ()fifice 3,329,753 Patented May 23, 19673,320,763 CONTROLS FOR REFRIGERATION SYSTEMS James R. Hamish, Staunton,Va., assignor to Westinghouse Electric Corporation, Pittsburgh, 'Pa., 2corporation of Pennsylvania Filed Nov. 19, 1965, Ser. No. 508,736 9Claims. (Cl. 62-197) This invention relates to controls forrefrigeration systems.

In my copending application, Ser. No. 447,008, filed Apr. 9, 1965, nowPatent No. 3,264,837, there is disclosed a refrigeration system using asub-cooling control valve as an expansion valve to over-feed anevaporator during normal operation, the sub-cooling control valve beingshunted by an automatic expansion valve responsive to the pressure ofthe refrigerant leaving the evaporator, for preventing the evaporatorfrom becoming starved during abnormal operation when the condensingpressure is insufiicient to properly operate the sub-cooling controlvalve. Such valves are not readily available for relatively largerefrigeration systems, and if available, their costs would be relativelyhigh.

A feature of this invention is that a relatively small, sub-coolingcontrol valve operates as a pilot valve to control a relatively largeexpansion valve during normal operation, with the sub-cooling controlvalve shunted by a relatively small automatic expansion valve whichoperates as a pilot valve to control the expansion valve during abnormaloperation when the condensing pressure is insufiicient to properlyoperate the sub-cooling control valve.

It is conventional to use a solenoid-operated valve in the high pressureliquid line of a refrigeration system to provide positive liquidshut-off during shut-downs of the system. In a relatively large system,a relatively large shut-01f valve is required. Another feature of thisinvention is that a relatively small, solenoid-operated, liquid shut-offvalve is used in the control line of the previously mentioned,relatively large expansion valve.

In a large refrigeration system, the over-load control setting of acompressor motor, and the high pressure cut-out setting, may be criticalbecause of pull-down requirements during warm start-ups when the outdoorambient temperature is relatively high, and one or both of such controlsmay turn the compressor motor off. Another feature of this invention isthat a relatively small, automatic expansion valve responsive to theevaporator pressure, is located in the control line of the previouslymentioned, large expansion valve, and operates t adjust the expansionvalve to starve the evaporator for preventing excessive pressures duringsuch warm startups.

An object of this invention is to use a relatively small, sub-coolingcontrol valve to control a relatively large expansion valve in arefrigeration system.

Another object of this invention is to use a relatively small, automaticexpansion valve to control a relatively large expansion valve in arefrigeration system.

Another object of this invention is to use a relatively small,sub-cooling control valve, shunted by a, relatively small, automaticexpansion valve, to control a relatively large expansion 'valve in arefrigeration system.

Another object of this invention is to prevent excessive refrigerantpressures in a refrigeration system during warm start-ups at highoutdoor ambient temperatures. This invention will now be described withreference to the annexed drawings, of which:

FIG. 1 is a diagrammatic view of a refrigeration system embodying thisinvention;

FIG. 2 is an enlarged side section of the automatic expansion valve ofFIG. 1;

FIG. 3 is an enlarged, side section of the sub-cooling control valve ofFIG. 1, and

FIG. 4 is an enlarged side section of the main expan .sion valve of FIG.1.

A conventional, hermetic, refrigerant compressor C having an enclosedelectric motor CM, is connected by discharge gas tube 10 to one end ofcondenser coil 11, the other end of which is connected by liquid tube12, through a heat exchange coil which is not shown, within accumulator13, to the inlet of main expansion valve 14. The outlet of the valve 14is connected by tube 15 to one end of evaporator coil 16, the other endof which is connected by tube 17 to the top of the accumulator 13. Theaccumulator 13 is connected by suction gas tube 18 to the suction sideof the compressor C. The components in the accumulator 13 are fullydisclosed in the previously mentioned application.

The tube 12 is also connected between the accumulator 13 and theexpansion valve 14 to tube 20 which is connected through valve 21 to theinlets of sub-cooling control valve 22 and automatic expansion valve 23operating as pilot valves. The outlets of the valves 22 and 23 areconnected by tube 24 through solenoid-operated valve 25 to the top ofpiston chamber 26 of the main expansion valve 14.

The valve 23 has a diaphragm chamber '30 with a diaphragm 31 extendingacross its center. The interior of the chamber 30 below the diaphragm 31is connected by capillary tube 32 to the tube 17. The valve 23 has apartition 34 extending across its interior between its inlet and outlet,with a valve opening 35 therein. A valve piston '36 below the opening35, is connected by piston rod 37 to the center of the diaphragm 31. Acoiled spring 38 extends between the center of the top of the diaphragm31 and the top of the chamber 30, and biases the piston 36 towards openposition.

The valve 21 is similar to the valve 23 except that it is adjusted toclose at a different pressure as will be described later, and has adiaphragm chamber 39, the lower portion of which is connected by acapillary tube 40 to the tube 32.

The sub-cooling control valve 22 has a diaphragm chamber 41 with adiaphragm 42 extending across its center. It has a partition 43extending across its interior between its inlet and outlet, with a valveopening 44 therein. A valve piston 45 above the opening 44 is connectedby piston rod 46 to the center of the diaphragm 42. A coiled spring 47extends around the rod 46 between the bottom of the chamber 41 and thetop of the valve piston 45, and biases the piston 45 towards closedposition. The interior of the chamber 41 above the diaphragm 42 isconnected by capillary tube 50 toa conventional thermal bulb 51 in heatexchange contact with the tube 12 between the accumulator 13 and thecoil 11. The interior of the chamber 41 below the diaphragm 42 isconnected by capillary tube 52 to the interior of the tube 12 adjacentto the bulb 51.

As shown by FIG. 4, the piston chamber 26 of the main expansion valve 14has a piston 55 slidable therein. A partition 56 extends across theinterior of the valve 14 between its inlet and outlet and has a valveopening 57 therein. A valve piston 58 below the opening 57 is connectedby piston rod 59 to the center of the piston 55. A coiled spring 60extends between the bottom of the piston 58 and the bottom of the valve14, and biases the piston 58 towards closed position. The piston 55 hasa pressure equalizing passage 61 extending therethrough.

Referring now to FIG. 1, a solenoid 65 is connected to the valve 25 toopen and close the latter. The compressor motor CM is connected toelectric supply line L1, and through switch S1 of motor starter MS, andwire 66 to electric supply line L2. The starter MS is connected throughswitch TS of thermostat T, and wires 67 and 68 to the lines L1 and L2.The solenoid 65 is connected by wire 69 and the wire 66 to the line L2,and is connected by wire I 76 and switch S2 of the starter MS to theline L1.

Operation When the thermostat T calls for cooling, it closes its switchTS which energizes the motor starter MS. The latter closes its switchesS1 and S2. The closed switch S1 energizes the compressor motor CM,starting the compressor C. The closed switch S2 energizes the solenoid65 which opens the valve 25. The compressor C supplies discharge gasthrough the tube 11) into the condenser coil 11. Refrigerant liquidflows from the coil 11 through the tube 12 and the heat exchange coil(not shown) within the accumulator 13, into the expansion valve 14 whichmeters refrigerant to the evaporator coil 16. Gas and unevaporatedliquid from the coil 16 flow through the tube 17 into the accumulator13. Gas separated from the liquid within the accumulator 13 flowsthrough the suction gas tube 18 to the suction side of they compressorC.

The valve 21 is adjusted to be open during normal operation so as topermit liquid to flow from the tube 12 into the inlets of the pilotvalves 22 and 23. It may be set to start to close when the pressure ofthe refrigerant leaving the evaporator coil 16 in a system using F22refrigerant increases, for example, above 84 p.s.i. as will be describedlater.

The pilot valve 23 is adjusted to be closed during normal operation whenthe evaporator pressure is normal, and to open when the evaporator coil16 is about to become starved as will be described later.

During normal operation, the sub-cooling control valve 22 adjust theexpansion valve 14 to meter refrigerant to the evaporator coil 16 at therate at which refrigerant is condensed in the condenser coil 11 whilemaintaining, for example, F. subcooling at a condensing temperature of100 F. An increase in the temperature of the liquid in the tube 12 atthe bulb 51, acts through the bulb 51, the capillary tube 50 and thediaphragm 42 of the valve 22, to adjust the piston 45 of the valve 22towards closed position, reducing the'liquid pressure above the piston55 of the valve 14, and causing the valve piston 58 of the valve 14 tomove towards closed position so as to back up more liquid within thecondenser coil 11, for increasing the sub-cooling of the liquid.Increased liquid pressure in the tube 12 where the capillary tube 52 isconnected-to the latter, acts through the tube 52 and the diaphragm 42to adjust the valve piston 45 of the valve 22 towards open position,increasing the liquid pressure above the piston 55 of the valve 14, andcausing the valve piston 58 of the valve 14 to move towards openposition. For an increase in the rate at which refrigerant is condensedin the coil 11, if the valve 14 is not sufficiently open, liquid in thecoil 11 will back up until the pressure is increased sutficiently or thetemperature is reduced sufliciently to cause the valve 22 to adjust thevalve 14 towards open position, and vice versa. When the condensing ratechanges, the valve 22 readjusts the valve 14 accordingly, but the lattermeters refrigerant to the evaporator coil 16 at the rate at whichrefrigerant is condensed in the condenser coil 11. The valve 14continuously overfeeds the evaportor coil 16 as disclosed in thepreviously mentioned application.

During abnormal conditions, such as at very low outambient temperaturesor other conditions resulting in abnormally low condensing pressures,the liquid subcooling at the bulb 51 may be insufiicient for the valve22 to adjust the expansion valve 14.sufi"1ciently open to prevent theevaporator coil 16 from becoming starved. At such times, the pilot valve23 responds through the capillary tube 32 to the resulting reducedpressure of the refrigerant within the tube 17 at the outlet of theevaporator coil 16, the reduced pressure below the diaphragm 31 of thevalve 23, permitting the spring 38 to move the piston 36 to openposition, supplying liquid above the piston 55 of the valve 14 to causethe valve piston 58 of the valve 14 to open sulficiently to providesufiicient refrjgerant to the evaporator coil 16 to prevent it frombecoming starved.

The bleed passage 61 in the piston 55 of the valve 14 permits pressurein the chamber above the piston 55 to equalize the evaporator pressurewhen the valve 22 or the valve 23 moves towards closed position, byflowing through the passage 61 :and the interior of the valve 14 intoits outlet, thus permitting the spring 60 to move the valve piston 58 ofthe valve 14 towards closed position.

On start-ups of the system, when the latter is a water chilling system,at an outdoor temperature of, say F., the chilled water temperature maybe 90 F. or even higher. This means that the compressor has to operateat very high suction pressures, and correspondingly high dischargepressures until the water has been chilled down to a temperature below55 F. The condenser would be sized to operate at an outdoor airtemperature of about F., but only when the temperature of thechilledwater leaving the chiller is at, say, 50 F. Consequently, warm start-upsduring high outdoor ambient temperatures, may result in the compressormotor being tripped out by an overload control or by a high pressurecut-out. The valve 21 prevents this. When the evaporator pressureincreases above 84 p.s.i., this pressure transmitted by the capillarytube 40 to the interior of the diaphragm chamber 39 of the valve21,.causes the valve 21 to throttle towards closed position, decreasingthe quantity of liquid supplied to the pilot valve 22 or 23 whichever isoperating, and. causing the valve 14 to throttle towards closed positionto starve the evaporator, thus preventing excessively high refrigerantpressures and compressor motor overload.

When the thermostat T is satisfied, it opens its switch TS, deenergizingthe motor starter MS which opens its switch S1, stopping the compressormotor CM. At the same time, the switch S2 of the starter MS opens,deenergizing the solenoid 65 which closes the valve 25 in the controltube 24 of the expansion valve 14, shutting off the supply of liquid tothe piston chamber 26 of the valve 14 so that the spring 60 closes thevalve piston 58. of'the valve 14, providing positive shutoff when thesystem is turned off.

Since the valves 21., 22, 23 and 25 are in the liquid supply to thepiston chamber 26 of the expansion valve 14, they can be relativelysmall valves, for example, three ton valves for controlling a onehundred ton valve 14.

While the invention has been disclosed as embodied in a non-reversiblesystem having condenser and evaporator coils, it may be used in heatpumps, and in systems in which the evaporators are water or other liquidchillers, and/ or in which the condensers are liquid cooled.

What is claimed is:

1. In a refrigeration system having a compressor, a condenser, anexpansion valve and an evaporator connected in series in a refrigerationcircuit; a pilot valve having an inlet connected to said circuit betweensaid condenser and said expansion valve to receive refrigerant liquidfrom said circuit, said pilot valve having an out let, said pilot valvehaving means including means responsive to the pressure and thetemperature of the refrigerant liquid leaving said condenser for openingand closing said pilot valve, said expansion valve having a chamberconnected to said outlet of said pilot valve for receiving refrigerantliquidv from said pilot valve 'when said pilot valve is open, and meansincluding means responsive to the pressure of the liquid entering said2. The invention claimed in claim 1 in which there is provided a secondpilot valve having an inlet connected to said inlet of said firstmentioned pilot valve and having an outlet connected to said outlet ofsaid first mentioned pilot valve, and in which said second pilot valvehas means including means responsive to the pressure of the refrigerantat said evaporator for opening said second pilot valve on a decrease inthe pressure of the refrigerant at said evaporator and for closing saidsecond pilot valve on an increase in the pressure of the refrigerant atsaid evaporator.

3. The invention claimed in claim 2 in which a liquid tube connects saidinlets of said pilot valves to said circuit, in which a second liquidtube connects said outlets of said pilot valves to said chamber, and inwhich a third pilot valve is connected in one of said tubes, said thirdvalve having means including means responsive to the pressure of therefrigerant at said evaporator for opening said third valve on adecrease in the pressure of the refrigerant at said evaporator and forclosing said third valve on an increase in the pressure of therefrigerant at said evaporator.

4. The invention claimed in claim 3 in which means is provided forstarting and stopping said compressor, in which a shut-off valve isconnected in one of said tubes, and in which means is provided forclosing said shut-01f valve when said compressor is stopped and foropening said shut-off valve when said compressoris started.

5. The invention claimed in claim 1 in which a liquid tube connects saidinlet of said pilot valve to said circuit, in which a second liquid tubeconnects said outlet of said pilot valve to said chamber, and in which asecond pilot valve is connected in one of said tubes, said second pilotvalve having means including means responsive to the pressure of therefrigerant at said evaporator for opening said second pilot valve on adecrease in the pressure of the refrigerant at said evaporator and forclosing said second pilot valve on an increase in the pressure of therefrigerant at said evaporator.

6. The invention claimed in claim 5 in which means is provided forstarting and stopping said compressor, in which a shut-off valve isconnected in one of said tubes, and in which means is provided forclosing said shut-01f valve when said compressor is stopped and foropening said shut-off valve when said compressor is started.

7, The invention claimed in claim 1 in which means is provided forstarting and stopping said compressor, ir which a liquid tube connectssaid inlet of said pilot valve to said circuit, in which a second liquidtube connect: said outlet of said pilot valve to said chamber, in whicla liquid shut-off valve is connected in one of said tubes, and in whichmeans is provided for closing said shut-ofi valve when said compressoris stopped and for opening said shut-off valve when said compressor isstarted.

8. In a refrigeration system having a compressor, a condenser, anexpansion valve and an evaporator connected in series in a refrigerationcircuit; a pilot valve having an inlet connected to said circuit betweensaid condenser and said expansion valve to receive refrigerant liquidfrom said circuit, said pilot valve having an outlet, said pilot valvehaving means including means responsive to the pressure of therefrigerant at said evaporator for opening said pilot valve on adecrease in the pressure of the refrigerant at said evaporator and forclosing said pilot valve on an increase in the pressure of therefrigerant at said evaporator, said expansion valve having a chamberconnected to said outlet of said pilot valve for receiving refrigerantliquid from said pilot valve when said pilot valve is open, and meansincluding means responsive to the pressure of the liquid entering saidchamber for adjusting said expansion valve towards open position on anincrease in the pressure of the liquid entering said chamber and foradjusting said expansion valve towards closed position on a decrease inthe pressure of the liquid entering said chamber.

9. The invention claimed in claim 8 in which means is provided forstarting and stopping said compressor, in which a liquid tube connectssaid inlet of said pilot valve to said circuit, in which a second liquidtube connects said outlet of said pilot valve to said chamber, in whicha liquid shut-01f valve is connected in one of said tubes, and in whichmeans is provided for closing said shut-off valve when said compressoris stopped and for opening said shut-off valve when said compressor isstarted.

References Cited by the Examiner UNITED STATES PATENTS 2,571,625 10/1951Seldon 62225 3,023,591 3/1962 Tilney 6221O X MEYER PERLIN, PrimaryExaminer,

1. IN A REFRIGERATION SYSTEM HAVING A COMPRESSOR, A CONDENSER, ANEXPANSION VALVE AND AN EVAPORATOR CONNECTED IN SERIES IN A REFRIGERATIONCIRCUIT; A PILOT VALVE HAVING AN INLET CONNECTED TO SAID CIRCUIT BETWEENSAID CONDENSER AND SAID EXPANSION VALVE TO RECEIVE REFRIGERANT LIQUIDFROM SAID CIRCUIT, SAID PILOT VALVE HAVING AN OUTLET, SAID PILOT VALVEHAVING MEANS INCLUDING MEANS RESPONSIVE TO THE PRESSURE AND THETEMPERATURE OF THE REFRIGERANT LIQUID LEAVING SAID CONDENSER FOR OPENINGAND CLOSING SAID PILOT VALVE, SAID EXPANSION VALVE HAVING A CHAMBERCONNECTED TO SAID OUTLET OF SAID PILOT VALVE FOR RECEIVING REFRIGERANTLIQUID FROM SAID PILOT VALVE WHEN SAID PILOT VALVE IS OPEN, AND MEANSINCLUDING MEANS RESPONSIVE TO THE PRESSURE OF THE LIQUID ENTERING SAIDCHAMBER FOR ADJUSTING SAID EXPANSION VALVE TOWARDS OPEN POSITION ON ANINCREASE IN THE PRESSURE OF THE LIQUID ENTERING SAID CHAMBER AND FORADJUSTING SAID EXPANSION VALVE TOWARDS CLOSED POSITION ON A DECREASE INTHE PRESSURE OF THE LIQUID ENTERING SAID CHAMBER.